diff --git a/README.rst b/README.rst
index b65a8ded8366ba5c42f68dff3c24382cc676c0ab..10ea16a40b25875a381f72f22bb61b51eb1f9a48 100644
--- a/README.rst
+++ b/README.rst
@@ -1,7 +1,8 @@
 Template
 ########
 
-A CLI tool for generating files from Jinja2 templates and environment variables.
+A CLI tool for generating files from Jinja2 templates and environment
+variables.
 
 Examples
 --------
@@ -11,6 +12,9 @@ Examples
     $ template -h
     usage: template [-h] [-o OUTPUT] [filename]
 
+    A CLI tool for generating files from Jinja2 templates and environment
+    variables.
+
     positional arguments:
       filename              Input filename
 
@@ -23,7 +27,7 @@ Examples
     Hello John.
     $ echo '{{ USER }}' > username.j2
     $ template --output username.txt username.j2
-    $ cat username
+    $ cat username.txt
     John
 
 
@@ -32,12 +36,12 @@ Jinja filters
 
 The following Jinja filters were added:
 
-- to_yaml: Convert to yaml.
-- from_yaml: Convert from yaml.
-- to_json: Convert to json.
-- from_json: Convert from json.
-- pprint: Pretty print variable.
-- combine: Combine 2 dictionaries.
+- :code:`to_yaml`: Convert to yaml.
+- :code:`from_yaml`: Convert from yaml.
+- :code:`to_json`: Convert to json.
+- :code:`from_json`: Convert from json.
+- :code:`pprint`: Pretty print variable.
+- :code:`combine`: Combine 2 dictionaries.
 
 Example usage can be seen in :code:`tests.sh`.
 
diff --git a/template/__init__.py b/template/__init__.py
index f476a5cdb163df62c18a565e4ed83f15fff5331d..3b0e5674ab6a6aa65de92ce9e9ccfadd062f2c06 100755
--- a/template/__init__.py
+++ b/template/__init__.py
@@ -21,7 +21,9 @@ def render(template_string):
 
 
 def main():
-    parser = ArgumentParser()
+    parser = ArgumentParser(
+        description='''A CLI tool for generating files from Jinja2 templates
+        and environment variables.''')
     parser.add_argument('filename',
                         help='Input filename',
                         type=argparse.FileType('r'),
diff --git a/template/filters.py b/template/filters.py
index 4fb5250089437896ba1ce20d3b9361c7fda780a6..018c9ac0422ab8a6a5ebf2e5949a4ce689a088ee 100644
--- a/template/filters.py
+++ b/template/filters.py
@@ -26,7 +26,7 @@ def pprint(value):
     return pformat(value)
 
 
-def combine(lefthand, righthand):
-    combined = lefthand.copy()
-    combined.update(righthand)
+def combine(default, override):
+    combined = default.copy()
+    combined.update(override)
     return combined
diff --git a/tests.sh b/tests.sh
index 256671433eedfa85fbd984211895af92d57aa2ad..fce6dc9113217902b4d93e15c5d0a304d0ca30ab 100755
--- a/tests.sh
+++ b/tests.sh
@@ -1,4 +1,5 @@
-#!/bin/sh -e
+#!/bin/sh
+set -eu
 
 export infile="$(mktemp)"
 export outfile="$(mktemp)"
@@ -36,5 +37,7 @@ echo '{{ [1, ] + [2, ] }}' > "$infile"
 test "$(template $infile)" = "[1, 2]"
 
 echo Testing combining dictionaries.
+echo '{{ {"a": 1, "b": 2}|combine({"a": 11, "c": 33}) }}' > "$infile"
+test "$(template $infile)" = "{'a': 11, 'c': 33, 'b': 2}"
 
 rm "$infile" "$outfile"